This invention relates to a cooling and heating system using a refrigerating apparatus of the absorption type.
Absorption type refrigerating apparatus use thermal energy as an energy source. In recent years, a cooling and heating system of the gas burning absorption type has come to attract attention, in view of the fact that a demand for electric power in the summertime has reached a peak load level due to popularization of electric cooling systems, and with a view to switching the energy source from oil to natural gas.
There are available a variety of combinations of a refrigerant and an absorbing agent used with absorption type refrigerating apparatus. The combinations that have been put to practical use include water and lithium bromide, ammonia and ammonia water, and Fron (CHCIF.sub.2) and tetraethyleneglycol dimethylether (CH.sub.3 O(CH.sub.2 CH.sub.2 O).sub.4 CH.sub.3), for example.
A gas burning absorption type cooling and heating system of the prior art referred to hereinabove includes in the refrigeration cycle a generator, a condenser, pressure reducing means, an evaporator, an absorber and a liquid pump as basic components. A heat source of a refrigerant of high temperature heated and separated at the generator serves as a heating heat source, and a latent heat source generated at the evaporator serves as a cooling heat source. This type of cooling and heating systems are disclosed in U.S. Pat. Nos. 3,527,061 and 3,638,452 to Roy W. Kruggel et al, U.S. Pat. No. 4,207,751 to Ottomar Kampfenkel et al. and Japanese Patent Application Laid-Open No. 53052/78 (Shozo Saito), for example. U.S. Pat. No. 3,527,061 contemplates performing a cooling and heating operation by switching the system between cold water and heated water circuits without effecting change-over of the refrigerant circuit. The refrigerant of elevated temperature separated at the generator is condensed into a liquid state at the condenser and fed to the evaporator after passing through the temperature type automatic expansion valve for pressure reduction and expansion, so as to cool the water flowing through the evaporator. In a cooling mode, the cooled water is supplied through a water channel change-over valve to a heat exchanger mounted in a spaced to be cooled, where heat exchange takes place between the water and air forcedly fed to the heat exchanger by a blower to cool the air. In a heating mode, the hot water flowing through the condenser is supplied through the water channel change-over valve to the heat exchanger mounted in the space to be heated, to effect heating of the space by heating air with the hot water. During the heating mode, frost formation takes place in an outdoor heat exchanger, when the operation is performed over a prolonged period. Defrosting can be carried out, however, by temporarily switching the water channel to a cooling operation.
In U.S. Pat. No. 3,638,452, no switching of the refrigerant circuit and the water circuit is effected and cooling and heating operations are performed by using cold water and hot water respectively. The refrigerant of elevated temperature separated at the generator is changed into a liquid stated by condensation at the condenser and supplied to the evaporator after having its pressure reduced by expansion, to cool the water flowing through the evaporator for use as a cooling heat source. For a heating heat source, the absorber, condenser and generator are formed into a water circuit for producing hot water.
In U.S. Pat. No. 4,207,751, no change-over of the refrigerant circuit is effected and a refrigerant is directly supplied, in a cooling mode, to a heat exchanger mounted in a duct leading to a space to be cooled, to directly cool the air. In a heating mode, the heat generated at the condenser and absorber is recovered through a hot water circuit, so as to provide a heating heat source.
Japanese Patent Application Laid-Open No. 53052/78 relies on the change-over of the refrigerant circuit for producing cold water and hot water for performing cooling and heating operations. In a cooling mode, the water cooled at the evaporator is used as a cooling heat source, and in a heating mode the evaporator is made to function as an absorber and an absorber is made to function as an evaporator, by switching the refrigerant circuit in some parts thereof.
Thus the cooling and heating systems using absorption type refrigerating apparatus of the prior art can be broadly classified into three types: one type produces cold water and hot water to provide heat sources for cooling and heating operations without effecting change-over of the refrigerant circuit; another type performs a cooling operation in a direct expansion system by causing heat exchange to take place between air and a refrigerant through a heat exchanger, and a heating operation by producing hot water by utilizing heat of absorption and heat of condensation, to use the hot water as a heating heat source; and still another type relies on the change-over of the refrigerant circuit to produce cold water and hot water, to make them serve as cooling and heating heat sources.
Generally, when a heat exchanger of the air cooling type is used, it is necessary to carry out defrosting in a heating mode because of frost formation. When defrosting is carried out, the system may be temporarily switched from the heating operation to a cooling operation as described in U.S. Pat. No. 3,527,061 referred to hereinabove. However, this process suffers the disadvantage that cold water is supplied to the indoor heat exchanger during a defrosting operation and the air in a space to be heated is temporarily cooled, so that the cold air ejected into the space makes people unpleasant and uncomfortable. To minimize the cold air blown into the space to keep the people from becoming uncomfortable, the number of revolutions of the blower may be decreased, the blower may be rendered totally inoperative or an auxiliary heat source, such as an electric heater, may be utilized to heat the ejected cold air, in a cooling and heating system of the air cooling heat pump type which uses a compressor. In some other cooling and heating systems of the compression type, a heating operation may be performed by using a plurality of heat exchangers while performing defrosting through one of the heat exchangers. This type has the disadvantage that it has a large size and the system becomes large in capacity, and the principle of operation cannot be incorporated in a system of small capacity.
Meanwhile heating and cooling systems of the water heat source and water cooling type would not satisfy the social needs because the water resources are running scarce and strict limitations are placed on their use.
In view of the foregoing, it is necessary that even an absorption type cooling and heating system be constructed as a heat pump type system of the air heat source and air cooling type, to meet the requirement of energy conservation.